Depressive symptoms are common in HIV patients and warrant thorough assessment and intervention. However, this may be made more critical by findings with regard to the effects of depression on immune function. Depression has been shown to adversely affect immune function; as well it may also accelerate the course of HIV disease progression. There is now evidence that depression not only influences key components of cellular immunity, but may increase the likelihood of disease progression. There is also very recent evidence that depression may alter the function of innate immunity among HIV+ women. Clearly, the impact of depression on immune function, particularly in HIV+ women, is clearly warranted. The central hypothesis of our study is that HIV-seropositive women who are diagnosed with major depression have a decreased function of natural killer (NK) cells and other cytotoxic effector cells, and that treatment with serotonin-specific reuptake inhibitors (SSRIs) reverses this decline. Further, we hypothesize that antidepressants will directly effect NK cell function. This accounts, at least in part for the recovery of function following treatment. If the hypotheses are supported, this could lead to an improved outcome for women with HIV disease. This project is intended to: 1. Determine the immune status especially the functional capacity of NK and cytotoxic T cells in women infected with HIV with and without co-morbid major depression 2. Determine the NK and T cell function from depressed women before and after treatment with an SSRI. 3. Study possible mechanisms by which treatment of depression in HIV infected women with an SSRI modulates NK cell function. The relationship between the modulation of NK function and improvement with an SSRI will be investigated.